Naomi Watts is the second-billed star in Jean-Marc Vallée’s Demolition. On the film’s official website, her name sits above the title next to Jake Gyllenhaal’s. Curiously, Watts barely appears in the film’s trailer. She’s onscreen for less than one second, and says just three words. (“You miss her?”) It’s almost like the trailer is trying to hide her.

To see the film is to understand why.

Watts’ character is one of the most baffling in any studio film in recent memory. At the center of Demolition is a strong lead performance by Jake Gyllenhaal, playing a man who loses his wife and then his mind. And just to Gyllenhaal’s right is Watts, playing this bizarre pot-smoking stalker who barges into his life with irrational and inexplicable behavior, and transforms what could be a moving portrait of grief into a grim collection of quirk.

Gyllenhaal plays Davis Mitchell, an investment banker who works for his father-in-law (Chris Cooper) at a successful Wall Street firm. He commutes to lower Manhattan from Long Island, where he lives in an ultra-modern dream house with this beautiful wife Julia (Heather Lind) — until Julia is killed in a car accident. Davis is miraculously unharmed, at least physically. Emotionally though, something seems broken. He feels nothing for his dead spouse. He goes to work and carries on as if nothing’s happened. But when a vending machine refuses to dispense his bag of Peanut M&Ms, Davis can’t let it go. He writes the vending machine company a letter and, with no one else to talk to, bares his soul. Then he writes another. And another.

That’s where Watts’ Karen comes in. She works in the customer service department of the vending machine company. Davis’ words move her. So she calls him — at two in the morning. Then she starts following him around Long Island and on his commute into New York City. (Apparently the vending machine company lets her set her own hours and come and go as she pleases.) Eventually Davis and Karen meet, and their relationship gets stranger. She takes him to Coney Island to buy weed and wax poetic about a decaying boardwalk carousel, then they run on the beach and flap their arms like birds. At one point, they build a fort out of couch cushions and some blankets and make shadow puppets. (It’s even worse than it sounds.)

While Karen obsesses over Davis, she neglects her troubled teenage son Chris (Judah Lewis), who’s been suspended from school for “telling the truth” about the War in Iraq in a social studies presentation. Meanwhile, Julia’s dad needs Davis to sign some papers so that he can start a scholarship in her honor, but his son-in-law keeps ducking him — along with the rest of his professional and personal obligations — to hang out with Karen and Chris, and to indulge his new favorite pastime: Breaking appliances, bathroom stalls, and even his own home, into millions of pieces.

Somewhere amidst this mess lies the potential for a powerful movie about loss, one not unlike Vallée’s Wild, in which a woman reeling from the death of her mother and the disintegration of her marriage walked the entire Pacific Crest Trail. Demolition tells a similar story about a wayward soul on a journey of self-discovery, and even employs a similar structure that blends past and present through evocative match cuts; a glance at a centerpiece might send Davis back to the moment years earlier when Julia first placed the centerpiece on their table.

Gyllenhaal shines in quiet moments, when the camera observes him processing his volatile emotions as he steps out of the shower or drives his car. But invariably things return to Watts’ manic pixie dream MILF and all of her outlandish baggage. It’s not that Watts’ performance is bad; it’s that her character, as conceived by Vallée and screenwriter Bryan Sipe, makes absolutely no sense. They keep piling on more twists and subtext — a shocking secret about a character here, a disjointed message about materialism or masculinity there — until Demolition turns into one of those Movies That Says Something Important About How We Live Now™ where nothing of importance is said, and none of the people onscreen resemble real, recognizable human beings.

There’s a kernel of an interesting idea here about a man who didn’t love his seemingly perfect life but doesn’t know how to cope with that truth once he confronts it. And Gyllenhaal’s work is strong enough that you wish the movie around him were better. But it isn’t. In one of his many rambling letters to the vending machine company, Davis notes that suddenly “for some reason, everything has become a metaphor” in his eyes. An uprooted tree reminds him of his life, and the storm that knocked over the tree reminds him of his loss, and a “DETOUR AHEAD” road sign reminds him of what he’s going through, and so on. In that spirit, the filmmakers should have taken a cue from their title and that central image of Gyllenhaal swinging a sledgehammer at everything in sight, and realized what had to be done.